The present invention relates generally to train brakes and, more particular, to a pneumatic control system for use with electronically controlled and non-electronically controlled train brakes.
Traditional train brakes utilize compressed air entering a brake cylinder to actuate each cars brakes. A normally pressurized brake pipe extends the entire length of the train and is used as a control signal such that a reduction in air pressure in the brake pipe causes the brakes to actuate. Each car has a reservoir of compressed air to power the brake cylinders. While the system has satisfactorily functioned in the past, certain deficiencies exist.
Due to the substantial length of many freight trains, the use of pressure drop as an actuation signal sometimes cause undesirable results. Specifically, a substantial amount of time is required for the pressure drop to propagate from car to car. The pressure drop propagation lag causes a corresponding delay in the application of brakes on each subsequent car. Unfortunately, the brake actuation delay increases the train stopping distance.
To avoid the time lag between first signaling for a brake application and when the last brakes apply, each of the car brakes would optimally apply simultaneously to achieve the shortest possible stopping distance. As such, electronically controlled brakes are highly desirable. Unfortunately, the cost of equipping each existing railway car with an electronic brake system is very high. Additionally, implementation of such a change would take years to achieve. It would also be difficult to assure that each and every car was equipped with the proper electronics.
Therefore, it is desirable to produce a pneumatic control system capable of using electronic or brake pipe pressure signals to actuate the brakes of a train car. Such a system is able to take advantage of electronically braked cars while also utilizing a brake pipe pressure drop to actuate the brakes in non-electronically controlled cars.
Accordingly, the pneumatic control system of the present invention operates in at least three separately definable modes. Firstly, the brake control system is operable without the use of electrical power. In this pneumatic mode, the brakes are actuated once a pressure drop in the brake pipe causes motion of certain pneumatic valves. Secondly, the brake control system of the present invention is operable in an electronically controlled pneumatics mode where each brake is operated via an electronic signal. Lastly, the system may operate in an emulation mode. Cars equipped with the pneumatic control system of the present invention operating in emulation mode electronically sense brake pipe pressure. Based on the rate of pressure drop, the brakes are actuated accordingly as will be described in greater detail hereinafter. The pneumatic control system also electronically signals a valve to exhaust the brake pipe on each car so equipped. The further exhaustion of brake pipe assists in sending the brake pipe signal down the train in an expedited manner. Cars in the train that are not equipped with the present invention will be signaled with a brake pipe pressure drop.